<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
    .boxA{
        background: #571a8d;
        width: 500px;
        height: 500px;
        border-radius: 50%;
        text-align: center;
        opacity:0.5;
        box-sizing: border-box;
        line-height: 500px;
        box-shadow:1px 2px 3px #d0d028;
    }
    </style>
</head>
<body>
<div class="boxA">
    这是一个盒子
</div>
</body>
</html>